Pancreatic cancer (PC) is the fourth leading cause of cancer-related deaths in North America, with a <6% five-year survival prognosis (Jemal et al., 2010; Li et al., 2008; Zhang et al., 2010). Understanding the mechanisms that give rise to PC pathogenesis and identifying prognostic marker signatures are critical for the development of new diagnostic and therapeutic strategies. The complex biological functions that give rise to cancer pathogenesis can rarely be attributed to individual molecules but rather arise from key interactions among various heterogeneous components interacting in modular regulatory networks, which result in a specific disease signature with far-reaching clinical effects (Bonnet et al., 2010; Hartwell et al., 1999). Described below are a multitude of individual molecules whose interactions were previously unknown, but are elucidate in the Detailed Summary.
Mesothelin (MSLN) is a cell surface glycoprotein overexpressed in ˜90% of human pancreatic adenocarcinomas (Argani et al., 2001; Bharadwaj et al., 2008; Li et al., 2008; Muminova et al., 2004). It was previously reported that MSLN overexpression leads to increased PC cell proliferation, invasion, and migration in vitro and increased tumor growth in vivo (Li et al., 2008). Yet little is known about the mechanisms through which MSLN overexpression gives rise to this aggressive phenotype. Further, several studies have identified roles for microRNAs (miRNAs) in PC pathogenesis. mRNAs are a group of small, non-coding RNA molecules that act as posttranscriptional regulators of messenger RNA activity and are frequently dysregulated in cancers (Garofalo et al., 2009). It has been postulated that a single miRNA can regulate several links of an entire functional network, and its dysregulation can therefore give rise to a complex disease phenotype (Wang et al., 2011). It was previously reported that MSLN constitutively activates NF-κB and promotes cell survival (Bharadwaj et al., 2011a; Bharadwaj et al., 2011b). OCT-2 is a bi-functional TF that can exert both activating and repressing functions in a context-dependent manner (Friedl and Matthias, 1995; Liu et al., 1996). Its expression was previously thought primarily restricted to B-cells. All tumor cell lines of the B-cell lineage express OCT-2, including Hodgkin's disease cells (Bargou et al., 1996) and non-Hodgkin's lymphoma (Pileri et al., 2003). ZEB1 is a crucial epithelial-to-mesenchymal transition (EMT) activator in human colorectal and breast cancer (Burk et al), and has been linked to increased EMT and chemoresistance in pancreatic cancers (Wang et al., 2009). ZEB1 also directly suppresses transcription of and is involved in a reciprocal regulatory loop with miRNAs in the miR-200 family (Burk et al, 2008). PBX-1 was initially identified as a participant in pre-B-cell acute lymphoblastic leukemia (Asahara et al., 1999; Dutta et al., 2001), has been associated with progression of melanoma, (Shiraishi et al., 2007) and is an inducer of the gene for VCP, a ubiquitously expressed protein involved in cell survival (Wang et al., 2004). VCP is associated with cancer growth and is a prognostic marker for PC metastasis (Asai et al., 2002; Yamamoto et al., 2004c; Yamamoto et al., 2004d; Yamamoto et al., 2004e).
The approach of studying a single molecule in an effort to identify effective anti-tumor targets is quickly being replaced by a system-wide approach to dissect the complex interactions between genes, RNA, and proteins in regulating tumor progression. Here, a unique perspective on the interplay between several factors in a functional network is presented, which approaches the study of the effects of a single, central microRNA from a network biology framework. This disclosure uncovers a novel functional interactome in PC, dissects the mechanisms through which a central miRNA can alter the molecular makeup of pancreatic tumors, and identifies a pattern of expression that correlates directly with patient prognosis and survival. Examined are the expression, mechanisms of regulation, and resulting functions of this regulatory interactome, linking together the influence of various seemingly heterogeneous tumorigenic factors as a modular unit in PC pathogenesis, with significant clinical implications. In addition clinically relevant treatments for PC are disclosed, as is a biomarker signature which predicts treatment response and prognosis of patients with PC.